Current-limiting electric circuit breaker



E. B. HEFT 3,394,329

CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER July 23, 1968 2 Sheets-Sheet 1 Filed Nov. 25. 1966 /NVNTOR ELDON B. HEF'T WW C -7 r A a 0 A T TOR/\IEY July 23, 1968 E. B. HEFT 3,394,329

CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER Filed Nov. 25. 1966 2 Sheets-Sheet 2 "f nvvsurore E1. mm B. fi/srr A TTORNEY United States Patent CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER Eldon B. Heft, West Hartford,,Conn., assignor to General Electric Company, a corporation of New York Filed Nov. 25, 1966, Ser. No. 596,878

" SClaims. (Cl. 335-201) My invention relates to electric circuit breakers, and more particularly to electric circuit breakers of the current-limiting type.

Electric circuit breakers, that is, devices providing electrical protection by the automatic opening movement of relatively separable contacts, have been known for many-years. Such circuit breakers ordinarily have been capable of acting-as a switch, that is, providing for the opening andclosing of a circuit at the will of the operator, and also of automatically opening the circuit upon the occurrence of predetermined abnormal current or voltage conditions through the circuit breaker. While the development of the current carrying and current interrupting capacity of such circuit breakers has been very rapid, with constant reduction in the overallsize and increase of current-carryingcapacity, nevertheless constant improvements in electrical distribution systems have increased the short-circuit delivering capacity of such systems at aneven greater rate. .As a result, until recently the use of electric circuit breakers to protect circuits connected to exceptionally high power capacity circuitshas not proved economical in comparison With the use of special current-limiting fuses or combinations of such current-limiting fuses and electric circuit breakers. Still more recently however, a new type of electric breaker has been developed which not only performsthe functions of prior art circuit breakers in acting as a switch and in automatically interrupting overload and minor short-circuit currents, but which is also capable of performing a current-limiting function. This, in effect, opens the door to the use of electric circuit breakers in electric power systems of not onlyexceptionally high, but of virtually unlimited-capacity, A current-limiting circuit breaker of the type referred to is disclosed, for example, in applicationSer. No. 457,557 filed May 21, 1965, by R. L. Hurtle and H. G. Willard and in application Ser. No. 491,840, filed Sept. 30, 1965, by E. B. Heft and J. F. Johnson, and assigned to the same assignee as the present invention.

Basically, such new current-limiting circuit breakers includemanual and automatic operating mechanism and current overload sensing mechanism, as found in the prior art circuit breakers, but in addition provide a supplementary mechanism for opening the contacts at ultra-high speed. Amongthe new problems posed by such currentlimiting circuit breakers, however is the fact that the ultra-high speed operation of the contacts causes the ejection of hot gases at very high speed, and in addition, creates an extremely loud noise and shock wave, requiring special muftling means. Accordingly, special arc-chute sound and flame mufile devices have been developed, such, for example, as disclosed in co-pending application Ser. No. 594,048, filed Nov. 14, 1966, by E. B. Heft and assigned to the same assignee as the present invention. These various component parts are advantageously arranged in compact manner as disclosed in co-pending application Ser. No. 597,118 filed Nov. 25, 1966, by E. B. Heft and R. Laubenheimer and also assigned to the same assignee as the present invention.

As disclosed in the aforesaid applications, the provision of a high-speed opening mechanism and an arc-chute sound and flame muffle device have added substantially to the overall length of the circuit breaker. With such increased number and size of component parts, it has been found that if conventional prior art enclosure construction techniques were used several disadvantages would result. Thus, in accordance with prior art techniques for enclosing circuit breakers of this type, a molded casing is provided usually including a molded base member having an elongated recess for each pole assembly of the circuit breaker, and a cooperating top or cover piece likewise having corresponding elongated recesses or chambers therein cooperating with those of the base to provide chambers for receiving the parts of each pole of the circuit breaker. A casing of the type referred to it is disclosed, for example, in prior Patents 3,084,326 Klein et al. dated Apr. 2, 1965 and 3,104,297 Powell et al. dated Sept. 17, 1963 and assigned to the same assignee as the present invention. These disadvantages include (1) the creation of exceptionally long, thin, unsupported molded housing sections which would be extremely diflicult to produce and of relatively high cost, (2) the length of the required molded parts would require special molds which would be extremely expensive, and (3) because of the dimensions of the parts, such a molded casing would have to be of such thickness in order to provide the required strength that the weight of the assembly would be extremely high.

It is an object of the present invention to provide supporting and enclosing means for an electric circuit breaker of the type described which is relatively compact in overall dimensions and relatively light in weight.

It is another object of the invention to provide such a supporting and enclosing means which is economical to manufactture.

It is a further object of the invention to provide a supporting and enclosing means for an electric circuit breaker of the type described which provides high strength in relatively thin wall section portions.

It is another object of the invention to provide supporting and enclosing means 'for a circuit breaker of the type described in which the molded parts required are not of excessive overall dimension in any one direction.

Other objects of the invention will in part become obvious and will in part be pointed out in the following detailed description, and the scope of the invention will be set forth in the appended claims.

In accordance with the invention, an electtric circuit breaker is provided including supporting and enclosing means comprising a generally planar :back plate support member, a plurality of unitary insulating supporting block assemblies supported on the main support plate and each adapted for a particular function with relation tto the overall function, and a generally channel-shaped thin-walled metallic cover portion providing the outer side walls and top wall of the complete enclosure and rigidly interconnected with the back plate to form a rigid enclosure.

In accordance with another aspect of the invention, the metallic channel-shaped enclosure cover includes a coating of insulating material strongly adhered thereto, and also carries an insulating shield at the top wall thereof surrounding the area through which the manual operating handle of the circuit breaker projects for additional protection to personnel from metallic parts.

The invention will be more clearly understood from the following detailed description. In the drawings,

FIGURE 1 is a perspective view of a current-limiting circuit breaker incorporating the invention;

FIGURE 2 is a perspective view similar to FIGURE 1, showing the cover portion thereof in exploded relation with portion thereof broken away;

FIGURE 3 is a side elevation view of the circuit breaker of FIGURE 1, the enclosing cover portion being shown in section.

Referring to the drawings, the invention is shown as incorporated in an electric circuit breaker including a generally U-shaped cross-sectional metallic sheet metal cover and a generally planar insulating back plate 11. Supported on the back plate 11 are a plurality of referring to FIGURE 2, a line terminal support block 12, a trip unit support block 13A, a mechanism support block 13 and a stationary contact and are chute support block 14, and a combination line terminal and are chute muffle support block 15. The blocks 12-15 inclusive are fixedly mounted on the back plate 11 y suitable means, such as screws, not shown, extending upwardly through the back wall.

The insulating block 12 serves to support a plurality of load terminals 16, there being one provided for each of the pole chambers of the circuit breaker (the embodiment illustrated is a three-pole circuit breaker and therefore there are three sets of line and load terminals).

The insulating block portion 13A serves to support a trip unit 17 which will be described in more detail later.

The insulating block 13 serves to support a manual and automatic operating mechanism designated generally by the numeral 18 and having an insulating handle portion 19. The insulating block 14 serves to support and position the stationary contact and are chute and 3-pole mufile assembly designated generally by the numeral 20.

The insulating block 15 serves to support and position a plurality of line terminals 21, and includes upstanding barrier portions comprising outer barrier portions 22 at each side of the circuit breaker, and intermediate barrier portions 23.

The operating mechanism may be of any suitable type adapted to perform the required functions, including the manual opening and closing of the contacts, the automatic opening of the contacts in response to mechanism release by the conventional trip unit 17, and automatic opening of the contacts despite the non-release of the mechanism 18 upon the actuation of a high-speed tripping means such for example as the high speed trip solenoid shown 25. A mechanism of the type described is disclosed and described in detail in co-pending application S.N. 596,637, filed Nov. 23, 1966, by J. F. Johnson and R. W. Laubenheimer and assigned to the same assignee as the present invention.

The solenoids 25 of each of the poles are separated from each other by insulating barrier plates 27, see FIGURE 2.

The trip unit 17 includes means for causing release of a latch normally holding the operating mechanism 18 in latched position, comprising inverse current-time sensing means for such example as a bimetallic strip, and magnetic sensing means such as a solenoid, not shown. A trip unit of the type described is disclosed and described in detail in Patent No. 3,162,739, issued Dec. 22, 1964 to K. W. Klein and D. B. Powell and assigned to the same assignee as the present invention.

The outer enclosure 10 is preferably constructed of metallic material such, for example, as steel, and includes an insulating coating 10A on all surfaces. In a preferred embodiment, for example, the insulating coating 10A comprises nylon which is applied by a fused-powder technique. While the outer enclosure is coated with in sulation on all surfaces in the preferred embodiment, it will be appreciated that instead, selected areas only may be insulated and the remainder left uninsulated.

The cover member 10 also has an opening 10' in the top wall thereof which is partially closed by an insulating shield member 29 rigidly afiixed to the top wall of the cover by suitable means, such as by screws or rivets 30. If desired, other means of attaching the shield 29, may be utilized, such for example as chemical bonding. The shield 29 includes an aperture 31 of smaller size, through which the insulating handle 19 projects, the opening 31 being otherwise closed by the enlarged inner portion 19A of the handle 19. The insulating shield 29 also serves to support an identification plate 32 suitably attached thereto. The insulating shield 29 further includes a plurality of generally circular apertures 33 providing access to adjusting members 34 of the trip unit 17.

The various insulating blocks and the insulating shield 29 are preferably formed by molding, facilitating high production at relatively low cost. Since these parts are individually not of excessive dimension in any one direction, molding by conventional techniques is economically feasible.

The current path through one pole of the circuit breaker will be described with reference to FIGURE 3. The current enters at the line terminal 21, passes through the elongated conductor 21A passing underneath the arc chute and mufile assembly 20, to relatively movable contacts, not shown, contained within the chamber 20. From the movable contacts, the current passes to a terminal 25A of the solenoid 25, thence to the solenoid 25 and to a conductor strap 25B passing under the mechanism 18 to the trip unit terminal 17A. The current then passes through the trip unit 17 to the load terminals 16. Upon the occurrence of predetermined current conditions, the current sensitive means Within the trip unit 17 is actuated, causing release of the latched mechanism 18 and automatic opening of the circuit breaker contact. Likewise the occurrence of excessive current conditions causes actuation of the solenoid 25 before the conventional trip unit 17 can respond and direct opening of the movable contacts.

In accordance with the invention, the various molded blocks and the insulating shield 29 may each be molded of an insulating material selected to be most suitable to the requirements for that particular part.

Although the supporting back plate 11 is comparatively thin, required rigidity is provided by the inter-connection of the generally U-shaped metallic cover 10 with the back plate 11 through the medium of the insulating blocks, which are rigidly fixed to the back plate 11, the attachment of the cover 10 to these blocks being performed by suitable means, such for example as by screws 36, see FIGURE 1.

It will be observed that I have provided a novel and highly effective enclosure construction and assembly for a multi-part electric circuit breaker, which occupies very small space. Thus, for example, the cross-sectional area taken up by the supporting and enclosing means over and above that required by the circuit breaker mechanism and other parts themselves is virtually negligible.

While the invention has been described in only one particular embodiment, it will be readily apparent that many modificaitons thereof may readily be made. Thus, for example, although the back support plate has been disclosed as comprising insulating material, I may instead utilize a metallic sheet with suitable insulating means, such, for example, as an insulating coating. Likewise, while the housing cover has been disclosed as comprising a metallic member coated with insulation, I may instead utilize a high-strength insulating material, such, for example as gloss-fiber reinforced polyester plastic for such cover.

It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desired to secure by Letters Patent of the United States is:

1. A multi-pole electric circuit breaker comprising:

(a) an elongated substantially planar back plate;

(b) an insulating terminal block supported at each end of said back plate, having a plurality of electrical I conductor connecting means supported thereon;

(c) a mechanism support block of insulating material supported on said back plate intermediate said terminal blocks and having a contact operating mechanism supported thereon;

(d) a trip unit support block supported on said back plate intermediate said mechanism support block and one of said terminal blocks, having a circuit breaker strip unit supported thereon;

(e) an arc-chamber support block supported on said back plate, having an arc chamber supported thereon; and

(f) a generally channel-shaped relatively thin-walled cover member substantially co-extensive with said back plate and enclosing all of said parts except said terminals.

2. An electric circuit breaker as set forth in claim 1, said circuit breaker also comprising means fixedly attaching each of said blocks to said back plate and means fixedly attaching said cover to at least some of said blocks.

3. An electric circuit breaker as set forth in claim 1 wherein said cover member comprises sheet metallic material having a coating of insulating material on both sides thereof.

4. An electric circuit breaker as set forth in claim 3 wherein said contact operating mechanism includes a manually-operable handle member projecting outwardly therefrom in a direction generally normal to said back plate and said cover member includes an opening in the bed of said channel and an insert of insuulating material at least partly closing said opening, said insert having an opening therein and said handle extending outwardly through said opening in said insert.

5. An electric circuit breaker as set forth in claim 1, said circuit breaker also comprising an electric solenoid for each pole of said circuit breaker positioned between said operating mechanism and said are chamber and an insulating barrier extending between adjacent ones of said solenoids generally normal to said back plate.

References Cited UNITED STATES PATENTS 2,457,023 12/1948 Zelt 200-168 2,863,969 12/1958 Edmunds 200133 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

1. A MULTI-POLE ELECTRIC CIRCUIT BREAKER COMPRISING: (A) AN ELONGATED SUBSTANTIALLY PLANAR BACK PLATE; (B) AN INSULATING TERMINAL BLOCK SUPPORTED AT EACH END OF SAID BACK PLATE, HAVING A PLURALITY OF ELECTRICAL CONDUCTOR CONNECTING MEANS SUPPORTED THEREON; (C) A MECHANISM SUPPORT BLOCK OF INSULATING MATERIAL SUPPORTED ON SAID PLATE INTERMEDIATE SAID TERMINAL BLOCKS AND HAVING A CONTACT OPERATING MECHANISM SUPPORTED THEREON; (D) A TRIP UNIT SUPPORT BLOCK SUPPORTED ON SAID BACK PLATE INTERMEDIATE SAID MECHANISM SUPPORT BLOCK AND ONE OF SAID TERMINAL BLOCK, HAVING A CIRCUIT BREAKER STRIP UNIT SUPPORTED THEREON; (E) AN ARC-CHAMBER SUPPORT BLOCK SUPPORTED ON SAID BACK PLATE, HAVING AN ARC CHAMBER SUPPORTED THEREON; AND (F) A GENERALLY CHANNEL-SHAPED RELATIVELY THIN-WALLED COVER MEMBER SUBSTANTIALLY CO-EXTENSIVE WITH SAID BACK PLATE AND ENCLOSING ALL OF SAID PARTS EXCEPT SAID TERMINALS. 